PDBsum entry 2aih

Hydrolase

PDB id: 2aih

Contents

Protein chain

67 a.a. *

Metals

_CL ×11

* Residue conservation analysis

PDB id:

2aih

Name:

Hydrolase

Title:

1h-nmr solution structure of a trypsin/chymotrypsin bowman-birk inhibitor from lens culinaris.

Structure:

Bowman-birk type protease inhibitor, lcti. Chain: a. Fragment: residues 43-109. Synonym: trypsin/chymotrypsin inhibitor

Source:

Lens culinaris. Lentil. Organism_taxid: 3864. Strain: macrosperma group. Tissue: seeds

NMR struc:

20 models

Authors:

E.M.Ragg,V.Galbusera,A.Scarafoni,A.Negri,G.Tedeschi,A.Consonni, F.Sessa,M.Duranti

Key ref:

E.M.Ragg et al. (2006). Inhibitory properties and solution structure of a potent Bowman-Birk protease inhibitor from lentil (Lens culinaris, L) seeds. Febs J, 273, 4024-4039. PubMed id: 16889634

Date:

29-Jul-05 Release date: 01-Aug-06

Protein chain

Q8W4Y8  (IBB_LENCU) -  Bowman-Birk type proteinase inhibitor from Lens culinaris

Seq: 110 a.a.

Struc: 67 a.a.

Febs J 273:4024-4039 (2006)

PubMed id: 16889634

Inhibitory properties and solution structure of a potent Bowman-Birk protease inhibitor from lentil (Lens culinaris, L) seeds.

E.M.Ragg, V.Galbusera, A.Scarafoni, A.Negri, G.Tedeschi, A.Consonni, F.Sessa, M.Duranti.

ABSTRACT

Bowman-Birk serine protease inhibitors are a family of small plant proteins, whose physiological role has not been ascertained as yet, while chemopreventive anticarcinogenic properties have repeatedly been claimed. In this work we present data on the isolation of a lentil (Lens culinaris, L., var. Macrosperma) seed trypsin inhibitor (LCTI) and its functional and structural characterization. LCTI is a 7448 Da double-headed trypsin/chymotrypsin inhibitor with dissociation constants equal to 0.54 nM and 7.25 nM for the two proteases, respectively. The inhibitor is, however, hydrolysed by trypsin in a few minutes timescale, leading to a dramatic loss of its affinity for the enzyme. This is due to a substantial difference in the kon and k*on values (1.1 microM-1.s-1 vs. 0.002 microM-1.s-1), respectively, for the intact and modified inhibitor. A similar behaviour was not observed with chymotrypsin. The twenty best NMR structures concurrently showed a canonical Bowman-Birk inhibitor (BBI) conformation with two antipodal beta-hairpins containing the inhibitory domains. The tertiary structure is stabilized by ion pairs and hydrogen bonds involving the side chain and backbone of Asp10-Asp26-Arg28 and Asp36-Asp52 residues. At physiological pH, the final structure results in an asymmetric distribution of opposite charges with a negative electrostatic potential, centred on the C-terminus, and a highly positive potential, surrounding the antitryptic domain. The segment 53-55 lacks the anchoring capacity found in analogous BBIs, thus rendering the protein susceptible to hydrolysis. The inhibitory properties of LCTI, related to the simultaneous presence of two key amino acids (Gln18 and His54), render the molecule unusual within the natural Bowman-Birk inhibitor family.